Paste for internal electrode and process for producing electronic part

ABSTRACT

An internal electrode paste comprises electrode material powder, a binder resin containing a polyvinyl butyral resin as the main component, and a solvent. The internal electrode paste furthermore comprises a plasticizer, and the plasticizer is contained by 25 parts by weight or more and 150 parts by weight or less with respect to 100 parts by weight of the binder resin. The binder resin is contained by 2.5 to 5.5 parts by weight with respect to 100 parts by weight of the electrode material powder. It is possible to provide an internal electrode paste having enough strength and an adhesive force for the dry transfer method, and a production method of an electronic device using the paste.

TECHNICAL FIELD

The present invention relates to a production method of an electronicdevice having an internal electrode, such as a multilayer ceramiccapacitor, and an internal electrode paste used in the productionmethod, and particularly relates to an internal electrode paste havingenough strength and adhesive force to enable dry transfer of an internalelectrode and a production method of an electronic device using thesame.

Background Art

In recent years, as a variety of electronic equipments become compact,electronic devices to be installed inside the electronic equipments havebecome more compact and higher in performance. As one of the electronicdevices, there is a ceramic electronic device, such as a CR built-insubstrate and a multilayer ceramic capacitor, and the ceramic electronicdevices have been required to be more compact and higher in performance.

To pursue a more compact ceramic electronic device having a highercapacity, there is a strong demand for making a dielectric layerthinner. Recently, a thickness of a dielectric green sheet composing adielectric layer has become a several μm or less.

To produce a ceramic green sheet, normally, a ceramic paste composed ofceramic powder, a binder (an acrylic resin and butyral based resin,etc.), a plasticizer (phthalate esters, glycols, adipic acids, andphosphoric esters) and an organic solvent (toluene, MEK and acetone,etc.) is prepared. Next, the ceramic paste is applied to a carrier sheet(a supporting body made by PET or PP) by the doctor blade method, etc.,heated and dried to produce.

Also, a method of producing by preparing a ceramic suspension whereinthe ceramic powder and binder are mixed in a solvent, then, extruding bytwin-screw a film-shaped molded item obtained by molding the suspensionhas been considered in recent years.

A method of producing a multilayer ceramic capacitor by using theceramic green sheet explained above will be explained in detail. Aninternal electrode conductive paste containing electrode material powderand a binder is printed to be a predetermined pattern on the ceramicgreen sheet and dried to form an internal electrode pattern. After that,the green sheet is peeled from the carrier sheet and stacked by apredetermined number of layers. Here, two methods are proposed, that area method of peeling the green sheet from the carrier sheet beforestacking in layers and a method of peeling the carrier sheet afterstacking in layers and adhering by compression, but the difference isnot large. Finally, the stacked body is cut to be chips, so that greenchips are prepared. After firing the green chips, external electrodesare formed, so that electronic devices, such as multilayer ceramiccapacitors, are produced.

When producing a multilayer ceramic capacitor, an interlayer thicknessof sheets formed with internal electrodes is in a range of 3 μm to 100μm or so based on a desired capacitance required as a capacitor. Also,in a multilayer ceramic capacitor, a part not formed with internalelectrodes is formed on an outer part in the stacking direction of thecapacitor chip.

In such a multilayer ceramic capacitor, it was general that a binderused in the green sheet paste was a polyvinyl butyral resin having apolymerization degree of 1000 or less (Mw=50,000) (refer to the JapanesePatent Publication No. 10-67567). As the reasons, to sufficiently secureadhesiveness of ceramic green sheets at the time of stacking, to reducesurface roughness of the green sheets, to secure plasticity of the greensheets, and to reduce viscosity of slurry may be mentioned. As aplasticizer, generally, phthalic acid, adipic acid, sebacic acid, andphosphoric esters can be used, which were selected in terms of a boilingpoint and hazardous property, etc. for the purpose of giving plasticity.

In recent years, as electronic equipments become more compact,electronic devices to be used therein have rapidly become more compact.In multilayer electronic devices as typified by a multilayer ceramiccapacitor, rapid development has been made on increasing the number oflayers to be stacked and attaining a thinner interlayer thickness. Torespond to the technical trends, a thickness of a green sheet, whichdetermines the interlayer thickness, has almost become 3 μm or less to 2μm or less. Also, along therewith, a thickness of the internal electrodelayer has become 1.5 μm or less, and the number of layers to be stackedhas almost become 300 or more.

To form an internal electrode on such a thin green sheet, when using theconventional printing method, there arises a problem of so calledsheet-attack that a solvent included in an internal electrode pastemelts the green sheet. Thus, the dry transfer method has been developed.

In the dry transfer method, first, a release layer is formed on a PETfilm as a supporting sheet and an internal electrode layer is printedthereon. Furthermore, to eliminate a level difference due to a thicknessof the internal electrode layer, a blank pattern layer having the samethickness as that of the internal electrode layer is formed on a blankpattern portion where an electrode is not formed.

A resin layer (adhesive layer) having adhesiveness is formed on adifferent PET film from the PET film formed with the internal electrodelayer, and transferred to the internal electrode layer and the blankpattern layer by thermo-compression bonding. Then, the PET film on theresin layer side is removed.

A dielectric green sheet is formed on a still other PET film andtransferred to the resin layer by heat transfer.

In this way, a release layer and an electrode are unified with the blankpattern layer, the resin layer and the green sheet, and the result isstacked successively, consequently, stacking of thin film sheets with nosheet-attack becomes possible.

A thickness of 0.1 μm or less of an adhesive layer used in the drytransfer method is effective to prevent delamination during the binderburnout. A butyral based resin is extremely effective to obtainsufficient strength and adhesive force even in the case of such anextremely thin layer.

An internal electrode paste used in the conventional printing method isoften composed of an ethyl cellulose based resin, metal powder and asolvent. However, since ethyl cellulose based resins were poor instrength and adhesiveness, there was a problem that electrode layerbreaking and an adhesive defect were easily caused in the dry transfermethod.

On the other hand, to make a chip capacitor to be more compact and havea larger capacity, an electrode layer has to be made thin and smooth aswell as thinning a dielectric layer.

Since metal weight per one layer becomes light as the electrode becomesthinner, a metal adhering amount has to be less when forming an internalelectrode layer by the printing method. It is advantageous in terms ofprocedure costs to decrease the metal adhering amount by lowering ametal content in the print paste in a conventional facility. However,when the solvent ratio is made high to lower the metal ratio, the pasteviscosity abruptly declines and it becomes impossible for a conventionalprinting facility to deal with.

Also, to improve smoothness of the internal electrode layer afterfiring, it is efficient to make the metal filling density high in theinternal electrode layer at the stage of green. To make the metalfilling rate high, an amount of other component, for example a binderresin, may be decreased. However, when the binder resin is decreased,the paste viscosity declines, so that it is necessary to use a binderhaving high viscosity.

DISCLOSURE OF THE INVENTION

The present invention was made in consideration of the abovecircumstances, and an object thereof is to provide an internal electrodepaste having enough strength and an adhesive force to perform drytransfer of an internal electrode, and being capable of improving themetal filling rate and smoothness of an internal electrode layer, and aproduction method of an electronic device using the same.

To attain the above object, an internal electrode paste according to thepresent invention comprises electrode material powder, a binder resincontaining a polyvinyl butyral resin and/or a polyvinyl acetal resin asthe main component, and a solvent.

The internal electrode paste of the present invention may contain otheradditives in addition to the electrode material powder, binder resin andsolvent.

In the case of forming an extremely thin internal electrode, when usinga conventionally general ethyl cellulose based resin as a binder resinof an internal electrode paste, an internal electrode layer formed afterdrying the paste has a poor adhesive force and transfer of an adhesivelayer becomes very difficult. Also, even when the adhesive layer can beadhered, because of the poor strength, the internal electrode layer iseasily damaged when peeling the PET film as a supporting sheet.

In the present invention, as a result that a polyvinyl butyral resinand/or a polyvinyl acetal resin is included in the internal electrodepaste, the internal electrode layer formed by the paste has highstrength and a high adhesive force, and transfer of an adhesive layer isrelatively easy. Also, breaking of the internal electrode layer is hardto be caused at the time of peeling the PET film as a supporting sheet.

The internal electrode paste of the present invention further contains aplasticizer, and the plasticizer is contained by 25 parts by weight ormore and 150 parts by weight or less with respect to 100 parts by weightof the binder resin. By adding a plasticizer, a release force of the PETfilm as a supporting sheet declines and a releasing operation becomeseasy. To obtain such an effect, an adding quantity of the plasticizer ispreferably 25 parts by weight or more. Note that when the addingquantity exceeds 150 parts by weight, an excessive plasticizer exudesfrom the internal electrode layer formed by using the paste, which isnot preferable.

A plasticizer able to be used in the internal electrode paste of thepresent invention is not particularly limited and preferably dioctyladipic acid (DOA), butyl phthalate butylene glycol (BPBG), didodecylphthalate (DDP), dibutyl phthalate (DBP), benzylbutyl phthalate (BBP),dioctyl phthalate (DOP) and dibutyl sebacate, etc. may be mentioned.

Preferably, the electrode material powder is contained by 50 wt % orless, more preferably less than 50 wt %, and particularly preferably 48wt % or less with respect to the entire internal electrode paste. Forexample, by lowering the content of the electrode material powder from50 wt % to 45 wt %, a thickness of the internal electrode can becomethinner by about 10% as far as an adhering amount as a paste is thesame, which contributes to make the layer thinner. Note that when thecontent of the electrode material powder is too small, the pasteviscosity abruptly declines, so that the content of the electrodematerial powder is preferably 40 wt % or more, and more preferably 43 wt% or more.

When the ratio of a solvent is made high to lower the content of theelectrode material powder in the internal electrode paste, the pasteviscosity declines and a problem of blur, etc. is easily caused whenprinting by using the paste. To maintain necessary viscosity whilekeeping the binder resin amount constant by making the solvent ratiohigh, it is efficient to use a resin having high viscosity.

In the present invention, a polyvinyl butyral resin and/or polyvinylacetal resin is used as a binder resin. There are a variety of grades inthese resins. In the present invention, by selecting a polyvinyl butyralresin and/or polyvinyl acetal resin having a polymerization degree of1400 or more, it is possible to maintain necessary viscosity even whenthe solvent ratio is made high. Note that a polymerization degree of agenerally produced polyvinyl butyral resin and/or polyvinyl acetal resinis 3600 or less. Accordingly, a preferable polymerization degree of thepolyvinyl butyral resin and/or polyvinyl acetal resin is 1400 to 3600.Note that the polymerization degree of the polyvinyl butyral resinand/or polyvinyl acetal resin may be 3600 or more.

In the present invention, a polyvinyl acetal resin is particularlypreferable. It is because it has higher viscosity at same polymerizationdegree comparing with that of a polyvinyl butyral resin. Note that in apolyvinyl acetal resin, when the acetalization degree is made high, theviscosity becomes high but dry density tends to decline.

An acetalization degree of a generally produced polyvinyl acetal resinis 50 to 74 mol % or so. In the present invention, the acetalizationdegree of the polyvinyl acetal resin is preferably 74 mol % or less, andmore preferably 66 mol % or less. When the acetalization degree becomeshigh, the dry density tends to decline, and continuity and smoothness ofelectrodes deteriorate after firing. Note that the lower theacetalization degree is, the more preferable, and the-lower limit may be50 mol % or less.

Preferably, the binder resin is contained by 2.5 to 5.5 parts by weightwith respect to 100 parts by weight of the electrode material powder.

Preferably, ceramic powder is furthermore contained. The ceramic powderis contained preferably by 1 to 20 wt %, and more preferably 2 to 15 wt% with respect to the entire paste. When the ceramic powder is toolittle, it is liable that matching of a dielectric layer and anelectrode layer is hard to be attained at the time of firing anddelamination is easily caused. While when it is too much, smoothness andcontinuity of electrodes are hindered.

In the case where the ceramic powder is contained in the paste, thebinder resin is preferable contained by 2.5 to 5.5 parts by weight withrespect to a total of 100 parts by weight of the electrode materialpowder and ceramic powder.

By lowering the binder resin ratio in the internal electrode paste, themetal filling density of the internal electrode layer before firingbecomes high, and smoothness of the internal electrode layer can bemaintained after firing. Accordingly, an amount of the binder resin ispreferably 5.5 parts by weight or less with respect to 100 parts byweight of pigment (electrode material powder and ceramic powder). Notethat when the binder resin is too little, the strength declines andbreaking of an internal electrode layer and other trouble arise in thedry transfer method. To obtain sufficient strength to perform the drytransfer method, a binder resin of 2.5 parts by weight or more isnecessary with respect to 100 parts by weight of the pigment. Note thatthe pigment is a combination of the electrode material powder andceramic powder when the ceramic powder is contained in addition to theelectrode material powder in the paste, and when the ceramic powder isnot contained, it only indicates the electrode material powder.

A production method of an electronic device according to the presentinvention comprises the steps of:

preparing the internal electrode paste as set forth in any one-of theabove;

forming a green sheet;

forming an internal electrode layer by using the internal electrodelayer paste;

stacking the green sheets via internal electrode layers to obtain agreen chip; and

firing the green chip.

Also, a production method of an electronic device of the presentinvention comprises the steps of:

forming an electrode layer on a surface of a first supporting sheet byusing the internal electrode paste as set forth in any one of theabove,;

pressing the electrode layer against a surface of a green sheet, andadhering the electrode layer to the surface of the green sheet;

stacking the green sheet adhered with the electrode layer to form agreen chip; and

firing the green chip.

Preferably, a binder resin included in the green sheet paste for formingthe green sheet contains a polyvinyl butyral resin, and a polymerizationdegree of the polyvinyl butyral resin is 1000 or higher and 1700 orlower, a butyralation degree of the resin is higher than 64 mol % andlower than 78 mol %, and the residual acetyl group amount is less than 6mol %.

When the polymerization degree of-the polyvinyl butyral resin is too lowin the green sheet paste, it is liable that sufficient mechanicalstrength as a green sheet is hard to be obtained when making the layerthin. While, when the polymerization degree is too high, the surfaceroughness declines when made to be a sheet. Also, when a butyralationdegree of the polyvinyl butyral resin is too low, solubility to thepaste tends to decline, while when too high, the sheet surface roughnesstends to deteriorate. Furthermore, when a residual acetyl group amountis too large, the sheet surface roughness tends to decline.

In the production method of an electronic device of the presentinvention, the internal electrode paste of the present inventionpreferably contains the same kind of a binder resin as the binder resincontained in a paste for forming a green sheet to be, for example, adielectric layer and a magnetic body layer after firing. This is thesame in the case of using an acrylic resin as a binder resin of thegreen sheet paste. By using the same kind of binder resin, control ofconditions in a binder removal step, etc. become easy.

BRIEF DESCRIPTION OF DRAWINGS

Below, the present invention will be explained based on embodimentsshown in drawings.

FIG. 1 is a schematic sectional view of a multilayer ceramic capacitoras an embodiment of the present invention;

FIG. 2A to FIG. 2C and FIG. 3A to FIG. 3C are sectional views of a keypart showing a transfer method of an electrode layer;

FIG. 4A to FIG. 4C, FIG. 5A to FIG. 5C, FIG. 6A to FIG. 6C, FIG. 7 andFIG. 8 are sectional views of a key part showing a stacking method of agreen sheet on which an electrode layer is adhered,

FIG. 9 is a graph showing relationship of an adding quantity of a binderresin and breaking strength of an internal electrode layer in examplesof the present invention, and

FIG. 10 is a graph showing relationship of an adding quantity of aplasticizer and release strength of a supporting sheet in the examplesof the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

First, as an embodiment of an electronic device produced according tothe present invention, an overall configuration of a multilayer ceramiccapacitor will be explained.

As shown in FIG. 1, a multilayer ceramic capacitor 2 according to thepresent embodiment comprises a capacitor element 4, a first terminalelectrode 6 and a second terminal electrode 8. The capacitor element 4comprises dielectric layers 10 and internal electrode layers 12, and theinternal electrode layers 12 are stacked alternately between thedielectric layers 10. The alternately stacked internal electrode layers12 on one side are electrically connected to inside of the firstterminal electrode 6 formed outside of one end portion of the capacitorelement 4. Also, the alternately stacked internal electrode layers 12 onthe other side are electrically connected to inside of the secondterminal electrode 8 formed outside of the other end portion of thecapacitor element 4.

In the present embodiment, an internal electrode layer 12 is formed bytransferring an electrode layer 12 a to a ceramic green sheet 10 a asshown in FIG. 2 to FIG. 6 as will be explained later on.

A material of the dielectric layer 10 is not particularly limited andcomposed of a dielectric material, for example, calcium titanate,strontium titanate and/or barium titanate, etc. A thickness of each ofthe dielectric layers 10 is not particularly limited, but those having athickness of several μm to several hundreds of μm are general.Particularly in the present embodiment, it is made to be thin aspreferably 5 μm or less, more preferably 3 μm or less, and particularlypreferably 1.5 μm or less. Also, the internal electrode layer 12 is madeto be thin as preferably 1.5 μm or less, more preferably 1.2 μm or less,and particularly preferably 1.0 μm or less.

A material of the terminal electrodes 6 and 8 is not particularlylimited, either, and copper, a copper alloy, nickel and a nickel alloy,etc. are normally used. Silver and an alloy of silver with palladium maybe also used. A thickness of the terminal electrodes 6 and 8 is notparticularly limited, either, but is normally 10 to 50 μm or so.

A shape and size of the multilayer ceramic capacitor 2 may be suitablydetermined in accordance with the object and use. When the multilayerceramic capacitor 2 has a rectangular parallelepiped shape, it isnormally a length (0.6 to 5.6 mm, preferably 0.6 to 3.2 mm)×width (0.3to 5.0 mm, preferably 0.3 to 1.6 mm)×thickness (0.1 to 1.9 mm,preferably 0.3 to 1.6 mm) or so.

Next, an example of production methods of the multilayer ceramiccapacitor 2 according to the present embodiment will be explained.

(1) First, a dielectric paste (green sheet paste) is prepared to producea ceramic green sheet for composing the dielectric layers 10 shown inFIG. 1 after firing.

The dielectric paste is composed of an organic solvent based pasteobtained by kneading a dielectric material (ceramic powder) and anorganic vehicle.

The dielectric material is suitably selected from a variety of compoundswhich become composite oxides or oxides, such as carbonates, nitrites,hydroxides, and organic metal compounds, and mixed for use. Thedielectric material is normally used as powder having an averageparticle diameter of 0.4 μm or less, and preferably 0.1 to 0.3 μm orless. Note that it is preferable to use finer powder than the greensheet thickness to form an extremely thin green sheet.

A binder used for the organic vehicle is not particularly limited and avariety of normal binders, such as ethyl cellulose, polyvinyl butyraland an acrylic resin, may be used, but a polyvinyl butyral resin is usedin the present embodiment. A polymerization degree of the polyvinylbutyral resin is 1000 or higher and 1700 or lower, and preferably 1400to 1700. Also, a butyralation degree of the resin is 64 mol % or higherand 78 mol % or lower, and preferably 64 mol % or higher and 70 mol % orlower, and the residual acetyl group amount is less than 6 mol % andpreferably 3 mol % or less.

An organic solvent to be used for an organic vehicle is not particularlylimited and an organic solvent, such as terpineol, butyl carbitol,acetone and toluene, etc. is used.

In the present invention, a dielectric paste may be also generated bykneading a dielectric material and a vehicle obtained by dissolving awater-soluble binder in water.

The water-soluble binder is not particularly limited and polyvinylalcohol, methyl cellulose, hydroxyethyl cellulose, a water-solubleacrylic resin and emulsion, etc. are used.

A content of each component in the dielectric paste is not particularlylimited and the dielectric paste can be fabricated to contain a solventof, for example, about 1 wt % to about 50 wt %.

In the dielectric paste, additives selected from a variety ofdispersants, plasticizers, dielectrics, subcomponent compounds, glassflit, and insulators may be included in accordance with need. Whenadding these additives, in the dielectric paste the total content ispreferably about 10 wt % or less. When using a butyral based resin as abinder resin, a content of a plasticizer is preferably about 25 to about100 parts by weight with respect to 100 parts by weight of the binderresin. When the plasticizer is too much, the plasticizer exudes and itbecomes difficult to handle, which is not preferable.

By using the dielectric paste, for example as shown in FIG. 3A, a greensheet 10 a is formed to be a thickness of preferably 0.5 to 30 μm, andmore preferably 0.5 to 10 μm or so on the carrier sheet 30 as a secondsupporting sheet by the doctor blade method, etc. The green sheet 10 ais dried after being formed on the carrier sheet 30. Temperature ofdrying the green sheet 10 a is preferably 50 to 100° C. and drying timeis preferably 1 to 20 minutes. A thickness of the green sheet 10 a afterdrying is contracted to 5 to 25% of that before drying. The thickness ofthe green sheet after drying is preferably 3 μm or less.

(2) As shown in FIG. 2A, a carrier sheet 20 as a first supporting sheetis prepared separately from the above carrier sheet 30, and a releaselayer 22 is formed thereon and, on top thereof, an electrode layer 12 ahaving a predetermined pattern is formed. On a surface of the releaselayer 22 where the electrode layer 12 a is not formed, a blank patternlayer 24 having substantially the same thickness as that of theelectrode layer 12 a is formed.

As the carrier sheets 20 and 30, for example, a PET film, etc. is used,and those coated with silicon, etc. are preferable to improve therelease property. Thicknesses of the carrier sheets 20 and 30 are notparticularly limited and are preferably 5 to 100 μm. The thicknesses ofthe carrier sheets 20 and 30 may be same or different.

The release layer 22 preferably contains the same dielectric powder asthe dielectric composing the green sheet 10 a shown in FIG. 3A. Also,the release layer 22 contains a binder, a plasticizer and a releaseagent other than the dielectric powder. A particle diameter of thedielectric powder may be the same as that of the dielectric particlesincluded in the green sheet but it is preferable to be smaller.

In the present embodiment, a thickness t2 of the release layer 22 ispreferably not more than a thickness of the electrode layer 12 a, andmore preferably, it is set to be a thickness of 60% or less, and furtherpreferably 30% or less.

A method of applying the release layer 22 is not particularly limited,but it has to be formed to be extremely thin, so that an applying methodusing, for example, a wire bar coater or a die coater is preferable.Note that adjustment of the release layer thickness can be made byselecting a wire bar coater having a different wire diameter. Namely, tomake the thickness of the release layer to be applied thinner, it can bedone by selecting one having a small wire diameter, inversely, to formit thick, one with a large wire diameter may be selected. The releaselayer 22 is dried after being applied. The drying temperature ispreferably 50 to 100° C. and the drying time is preferably 1 to 10minutes.

A binder for the release layer 22 is composed, for example, of anacrylic resin, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol,polyolefin, polyurethane, polystyrene, or an organic composed of acopolymer of these or emulsion. The binder contained in the releaselayer 22 may be the same as the binder contained in the green sheet 10 aor may be different from that, but preferably the same.

A plasticizer for the release layer 22 is not particularly limited and,for example, phthalate ester, dioctyl phthalate, adipic acid, phosphateester and glycols, etc. may be mentioned. The plasticizer to becontained in the release layer 22 may be the same as that contained inthe green sheet 10 a or may be different from that.

A release agent for the release layer 22 is not particularly limitedand, for example, paraffin, wax and silicone oil, etc. may be mentioned.A release agent contained in the release layer 22 may be the same asthat contained in the green sheet 10 a or may be different from that.

A binder is contained in the release layer 22 by preferably 2.5 to 200parts by weight, more preferably 5 to 30 parts by weight, andparticularly preferably 8 to 30 parts by weight or so with respect to100 parts by weight of dielectric particle.

A plasticizer is preferably contained in the release layer 22 by 0 to200 parts by weight, preferably 20 to 200 parts by weight, and morepreferably 50 to 100 parts by weight with respect to 100 parts by weightof the binder.

A release agent is preferably contained in the release layer 22 by 0 to100 parts by weight, preferably 2 to 50 parts by weight, and morepreferably 5 to 20 parts by weight with respect to 100 parts by weightof the binder.

After forming the release layer 22 on the surface of the carrier sheet30, as shown in FIG. 2A, an electrode layer 12 a to compose an internalelectrode layer 12 after firing is formed to be a predetermined patternon the surface of the release layer 22. A thickness of the electrodelayer 12 a is preferably 0.1 to 5 μm, and more preferably 0.1 to 1.5 μmor so. The electrode layer 12 a may be configured by a single layer ortwo or more layers having different compositions.

The electrode layer 12 a can be formed on the surface of the releaselayer 22 by a thick film formation method, such as a printing methodusing an electrode paste, or a thin film method, such as evaporation andsputtering. When forming the electrode layer 12 a on the surface of therelease layer 22 by a screen printing method or a gravure printingmethod as a kind of thick film method, it is as below.

First, an electrode paste is prepared. The electrode paste is fabricatedby kneading a electrode material powders composed of a variety ofconductive metals and alloys, or a variety of oxides, organic metalcompounds or resinates, etc. to be conductive materials after firingwith an organic vehicle.

As a conductive material (electrode material powder) to be used whenproducing an electrode paste, Ni, a Ni alloy, furthermore, a mixture ofthese are used. A shape of such a conductive material is notparticularly limited and may be a spherical shape and scale-like shape,etc. or a mixture of these shapes. In the case of a spherical shape,normally those having an average particle diameter of the conductivematerial of normally 0.01 to 2 μm, and preferably 0.05 to 0.5 μm or somay be used.

An organic vehicle contains a binder and a solvent. As the binder, forexample, ethyl cellulose, an acrylic resin, polyvinyl butyral, polyvinylacetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene, or acopolymer of these may be mentioned. In the present embodiment,particularly, butyral based resins, such as a polyvinyl butyral resinand/or a polyvinyl acetal resin, are preferable.

A binder resin is contained preferably by 2.5 to 5.5 parts by weightwith respect to 100 parts by weight of a conductive material (electrodematerial powder) in the electrode paste. In the electrode paste, thesame ceramic powder (inhibitor for sintering electrode) as the ceramicpowder may be contained in the green sheet paste. In that case, thebinder resin is contained in the electrode paste by preferably 2.5 to5.5 parts by weight with respect to 100 parts by weight of a totalweight of a conductive material (electrode material powder) and ceramicpowder (inhibitor for sintering electrode). When the binder resin is toolittle, the strength declines and breaking of an electrode layer 12 aand other trouble tend to arise in the dry transfer method, while whenthe binder resin is too much, the metal filling density of the electrodelayer 12 a before firing declines, and it tends to become difficult tomaintain smoothness of the internal electrode layer 12 after firing.

Preferably, dielectric material powder is contained by 50 wt % or lesswith respect to the entire internal electrode paste. For example, bylowering the content of the electrode material powder from 50 wt % to 45wt %, as far as an adhering amount as a paste is same, a thickness ofthe internal electrode layer 12 a can be made less by about 10% or so,which contributes to make the layer thinner.

Viscosity of an electrode paste composition measured by using an RV20type cone disc viscometer made by HAAKE when giving rotation ofobtaining a shear rate of 8[1/s] at 25° C. is 4 Pa.s or more, andpreferably 6 Pa.s or more. When the viscosity at a low share rate islow, blur is easily caused when printed.

When the ratio of a solvent is made high to lower the content of theelectrode material powder in the internal electrode paste, viscosity ofthe paste declines and blur and other problems are easily caused whenprinting by using the paste. To maintain necessary viscosity whilekeeping the binder resin amount constant by making the solvent ratiohigh, it is effective to use a resin having high viscosity.

In the present embodiment, as a binder resin for an internal electrodepaste, a polyvinyl butyral resin and/or a polyvinyl acetal resin isused. There are a variety of grades in these resins. In the presentembodiment, by selecting a polyvinyl butyral resin and/or polyvinylacetal resin having a polymerization degree of 1400 or more, it ispossible to maintain necessary viscosity even when the solvent ratio ismade high. Note that a polymerization degree of a generally producedpolyvinyl butyral resin and/or polyvinyl acetal resin is 3600 or less.Accordingly, a polymerization degree of the polyvinyl butyral resinand/or polyvinyl acetal resin is preferably 1400 to 3600 in the binderresin for the internal electrode paste. In the present embodiment,polyvinyl acetal is preferable, and those having an acetalization degreeof 74 mol % or less are preferable.

As a solvent, any of those well-known, for example, terpineol, dihydroterpineol, butylcarbitol and kerosene, etc. may be used. A solventcontent is preferably 20 to 50 wt % or so with respect to the entirepaste.

To improve the adhesiveness, the electrode paste preferably contains aplasticizer. As a plasticizer, benzylbutyl phthalate (BBP) and otherphthalate esters, adipic acids, phosphoric esters and glycols, etc. maybe mentioned. In the present embodiment, preferably, dioctyl adipic acid(DOA), butyl phthalate butylene glycol (BPBG), didodecyl phthalate(DDP), dibutyl phthalate (DBP), benzylbutyl phthalate (BBP), dioctylphthalate (DOP), and dibutyl sebacate, etc. are used. Among them,dioctyl phthalate (DOP) is particularly preferable.

The plasticizer is contained by preferably 25 parts by weight or moreand 150 parts by weight or less, and more preferably 25 to 100 parts byweight with respect to 100 parts by weight of a binder resin. By addinga plasticizer, an adhesive force of an electrode layer 12 a formed byusing the paste is improved, and an adhesive force of the electrodelayer 12 a and a green sheet 10 a improves. To obtain the effect, anadding quantity of the plasticizer is preferably 25 parts by weight ormore. Note that when the adding quantity exceeds 150 parts by weight, anexcessive plasticizer exudes from the electrode layer 12 a formed byusing the paste, which is not preferable.

After or before forming an electrode paste layer in a predeterminedpattern on a surface of the release layer 22 by the printing method, ablank pattern layer 24 having substantially the same thickness as thatof the electrode layer 12 a is formed on the surface of the releaselayer 22 not formed with the electrode layer 12 a. The blank patternlayer 24 is formed by the same method by using the same paste as thatfor forming the green sheet 10 a show in FIG. 3A except for whatexplained below.

A dielectric paste for forming the blank pattern layer contains abinder, a plasticizer and a release agent as an optional component inaddition to dielectric particles. A particle diameter of dielectricparticles may be the same as or different from that of the dielectricparticles contained in a ceramic green sheet.

As a binder, for example, an acrylic resin, polyvinyl butyral, polyvinylacetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene oremulsion of these may be used.

The binder contained in a dielectric paste for forming the blank patternlayer may be the same as or different from a binder contained in theceramic green sheet. Also, the binder contained in the dielectric layerpaste for forming the blank pattern layer may be the same as ordifferent from that in the electrode paste, but preferably, the samebinder is used.

A plasticizer contained in the dielectric paste for forming the blankpattern layer is not particularly limited and, for example, phthalateesters, adipic acids, phosphoric esters, and glycols, etc. may bementioned. A plasticizer contained in the dielectric paste for formingthe blank pattern layer may be the same as or different from theplasticizer contained in the ceramic green sheet.

The dielectric paste for forming the blank pattern layer contains aplasticizer by about 0 parts by weight to about 200 parts by weight,preferably about 20 parts by weight to 200 parts by weight, and morepreferably about 50 parts by weight to about 100 parts by weight withrespect to 100 parts by weight of the binder.

A release agent contained in the dielectric paste for forming the blankpattern layer is not particularly limited and, for example, paraffin,wax and silicone oil, etc. may be mentioned.

The dielectric paste for forming the blank pattern layer contains arelease agent by about 0 parts by weight to about 100 parts by weight,preferably about 2 parts by weight to 50 parts by weight, and morepreferably about 5 parts by weight to about 20 parts by weight withrespect to 100 parts by weight of the binder.

Viscosity of a paste for the blank pattern paste measured by using anRV20 type cone disc viscometer made by HAAKE when giving rotation ofobtaining a shear rate of 8[1/s] at 25° C. is 4 Pa.s or more, andpreferably 7 Pa.s or more. When the viscosity at a low share rate islow, blur is easily caused when printed.

The blank pattern paste is printed on a blank pattern portion betweenelectrode layers 12 a as shown in FIG. 2A. After that, the electrodelayer 12 a and the blank pattern layer 24 are dried in accordance withneed. The drying temperature of the electrode layer 12 a and the blankpattern layer 24 is not particularly limited and is preferably 70 to120° C., and drying time is preferably 1 to 10 minutes.

(3) As shown in FIG. 2A, an adhesive layer transfer sheet formed with anadhesive layer 28 is prepared on the surface of a carrier sheet 26 as athird supporting sheet separately from the carrier sheets 20 and 30explained above. The carrier sheet 26 is formed by the same sheet asthat of the carrier sheets 20 and 30.

The adhesive layer includes a binder and a plasticizer. The adhesivelayer 28 may contain the same dielectric particle as that of thedielectrics composing the green sheet 10 a, however, in the case offorming an adhesive layer having a thinner thickness than a particlediameter of the dielectric particles, it is better not to containdielectric particles. Also, when dielectric particles are contained inthe adhesive layer 28, a particle diameter of the dielectric particlesis preferably smaller than the particle diameter of the dielectricparticles contained in the green sheet.

A plasticizer is preferably contained in the adhesive layer 28 by 0 to200 parts by weight, preferably 20 to 200 parts by weight, and morepreferably 50 to 100 parts by weight with respect to 100 parts by weightof the binder.

A thickness of the adhesive layer 28 is preferably 0.02 to 0.3 μm or so,more preferably, thinner than an average particle diameter of dielectricparticles contained in the green sheet. Also, a thickness of theadhesive layer 28 is preferably 1/10 or less of a thickness of the greensheet 10 a.

When a thickness of the adhesive layer 28 is too thin, the adhesiveforce declines, while when too thick, a space is easily formed inside anelement body after sintering depending on the thickness of the adhesivelayer, and a capacitance by an amount of the volume tends to decreaseremarkably.

The adhesive layer 28 is formed on the surface of the carrier sheet 26as a third supporting sheet, for example, by a bar coater method, diecoater method, reverse coater method,-dip coater method and kiss coatermethod, etc. and dried in accordance with need. The drying temperatureis not particularly limited, but is preferably the room temperature to80° C., and the drying time is preferably 1 to 5 minutes.

(4) To form the adhesive layer on the surface of the electrode layer 12a and the blank pattern layer 24 shown in FIG. 2A, a transfer method isapplied in the present embodiment. Namely, as shown in FIG. 2B, theadhesive layer 28 of the carrier sheet 26 is pressed against the surfaceof the electrode layer 12 a and the blank pattern layer 24, heated andpressed, then, the carrier sheet 26 is removed. Consequently, as shownin FIG. 2C, the adhesive layer 28 is transferred to the surface of theelectrode layer 12 a and the blank pattern layer 24. Note that transferof the adhesive layer 28 may be performed on the surface of the greensheet 10 a shown in FIG. 3A.

The heating temperature at transferring is preferably 40 to 100° C., andthe pressing force is preferably 0.2 to 15 MPa. Pressing may beperformed by a press or a calendar roll, but is preferably performed bya pair of rolls.

After that, the electrode layer 12 a is adhered to the surface of thegreen sheet 10 a formed on the surface of the carrier sheet 30 shown inFIG. 3A. For that purpose, as shown in FIG. 3B, the electrode layer 12 aand the blank pattern layer 24 of the carrier sheet 20 are pressed viaadhesive layer 28 against the surface of the green sheet 10 a togetherwith the carrier sheet 20, heated and pressed. As a result, as shown inFIG. 3C, the electrode layer 12 a and the blank pattern layer 24 aretransferred to the surface of the green sheet 10 a. Note that since thecarrier sheet 30 on the green sheet side is peeled off, when seeing fromthe green sheet 10 a side, the green sheet 10 a is transferred to theelectrode layer 12 a and the blank pattern layer 24 via the adhesivelayer 28.

Heating and pressing at the time of transferring may be pressing andheating by a press or by a calendar roll, but is preferably performed bya pair of rolls. The heating temperature and the pressing force are sameas those at the time of transferring the adhesive layer 28.

A single-layer electrode layer 12 a in a predetermined pattern is formedon the single green sheet 10 a by steps shown in FIG. 2A to FIG. 3C. Agreen sheet 10 a formed with the electrode layer 12 a is stacked byrepeating the steps shown in FIG. 4A to FIG. 6C. Note that the samereference numbers are given to common members with those shown in FIG.3A to FIG. 4C, and an explanation thereon is partially omitted.

First, as shown in FIG. 4A to FIG. 4C, the adhesive layer 28 istransferred to the surface on the other side of the electrode layer(back side) on the green sheet 10 a. After that, as shown in FIG. 5A toFIG. 5C, the electrode layer 12 a and the blank pattern layer 24 aretransferred to the back side of the green sheet 10 a via the adhesivelayer 28.

Next, as shown in FIG. 6A to FIG. 6C, on the surface of the electrodelayer 12 a and the blank pattern layer 24, the green sheet 10 a istransferred via the adhesive layer 28. After that, by repeating thetransfer, a multilayer block, wherein a large number of electrode layers12 a and the green sheet 10 a are alternately stacked as shown in FIG.7, is obtained.

Note that without applying the steps shown in FIG. 5C to FIG. 6C, thatis, from the step shown in FIG. 5B, not to remove the carrier sheet 20on the lower side but to remove the carrier sheet on the upper side, anda multilayer unit U1 shown in FIG. 4C may be stacked thereon. Afterthat, by repeating an operation of removing the carrier sheet 20 on theupper side again, stacking thereon the multilayer unit U1 shown in FIG.4C, and removing the carrier sheet 20 on the upper side, a multilayerblock wherein a large number of electrode layers 12 a and the greensheet 10 a are alternately stacked as shown in FIG. 7 is obtained. Amethod of stacking the multilayer unit U1 shown in FIG. 4C is superiorin terms of an efficiency of the stacking operation.

When the number of stacking layers of the green sheet is small, a firingstep in the next step is performed by the multilayer block alone. Also,in accordance with need, a plurality of multilayer blocks as such may bestacked via adhesive layers 28 formed by a transfer method in the sameway as above to obtain a multilayer body having larger number of layers.

(5) After that, as shown in FIG. 8, a green sheet 40 for an outer layer(a thick multilayer body obtained by stacking a plurality of greensheets not formed with an electrode layer) is stacked on the lowersurface of the stacked body and the entire stacked body is supported byan absorption holder 50. After that, the carrier sheet 20 on the upperside is peeled off, the green sheet 40 for an outer layer is formed ontop of the multilayer body in the same way, and final pressing isperformed.

Pressure at the time of the final pressing is preferably 10 to 200 MPa.Also, the heating temperature is preferably 40 to 100° C. After that,the multilayer body is cut to be a predetermined size to form greenchips. The green chips are subjected to binder removal processing andfiring processing, then, thermal treatment is performed in order tore-oxidize the dielectric layer.

The binder burn-out processing may be performed under a normalcondition, but when using a base metal, such as Ni and a Ni alloy, as aconductive material of the internal electrode layer, it is preferablyperformed under the specific condition below.

temperature rising rate: 5 to 300° C./hour, particularly 10 to 50°C./hour

holding temperature: 200 to 800° C., particularly 350 to 600° C.

holding time: 0.5 to 20 hours, particularly 1 to 10 hours

atmosphere: a mixed gas of wet N₂ and H₂

A firing condition is preferably as below.

temperature rising rate: 50 to 500° C./hour, particularly 200 to 300°C./hour

holding temperature: 1100 to 1300° C., particularly 1150 to 1250° C.

holding time: 0.5 to 8 hours, particularly 1 to 3 hours

cooling rate: 50 to 500° C./hour, particularly 200 to 300° C./hour

atmosphere gas: a mixed gas of wet N₂ and H₂, etc.

Note that oxygen partial pressure in an atmosphere at firing ispreferably 10⁻² Pa or less, particularly 10⁻² to 10⁻⁸ Pa. When exceedingthe above ranges, the internal electrode layer tends to oxidize, whilewhen the oxygen partial pressure is too low, abnormal sintering iscaused in an electrode material of the internal electrode layer to bebroken.

The thermal treatment after performing such firing is preferablyperformed with a holding temperature or highest temperature of 1000° C.or higher, more preferably 1000 to 1100° C. When the holding temperatureor the highest temperature at the time of the thermal treatment is lowerthan the above ranges, it is liable that oxidization of the dielectricmaterial is insufficient to make the insulation resistance lifetimeshort, while when exceeding the above ranges, Ni in the internalelectrode oxidizes and the capacity decreases, moreover, Ni reacts witha dielectric base and the lifetime also tends to become short. Theoxygen partial pressure at the time of thermal treatment is higher thana higher oxygen partial pressure than a reducing atmosphere at the timeof firing, preferably 10⁻³ Pa to 1 Pa, and more preferably 10⁻² Pa to 1Pa. When it is lower than the above range, re-oxidization of thedielectric layer 2 becomes difficult, while when exceeding the aboveranges, the internal electrode layer 3 tends to oxidize. Other conditionof the thermal treatment is preferably as below.

holding time: 0 to 6 hours, particularly 2 to 5 hours

cooling rate: 50 to 500° C./hour, particularly 100 to 300° C./hour

atmosphere gas: wet N₂ gas, etc.

Note that to wet a N₂ gas or a mixed gas, etc., for example, a wetter,etc. may be used. In this case, the water temperature is preferably 0 to75° C. or so. Also, the binder removal processing, firing and thermaltreatment may be performed continuously or separately. When performingcontinuously, the atmosphere is changed without cooling after the binderremoval processing, continuously, the temperature is raised to theholding temperature at firing to perform firing. Next, it is cooled andthe thermal treatment is preferably performed by changing the atmospherewhen the temperature reaches to the holding temperature of the thermaltreatment. On the other hand, when performing them separately, afterraising the temperature to the holding temperature at the binder removalprocessing in an atmosphere of a N₂ gas or a wet N₂ gas, the atmosphereis changed, and the temperature is furthermore raised for firing. Aftercooling the temperature to the holding temperature at the thermaltreatment, it is preferable that the cooling continues by changing theatmosphere again to a N₂ gas or a wet N₂ gas. Also, in the thermaltreatment, after raising the temperature to the holding temperatureunder the N₂ gas atmosphere, the atmosphere may be changed, or theentire process of the thermal processing may be in a wet N₂ gasatmosphere.

The thus obtained sintered body (element body 4) is subjected to endsurface polishing, for example, by barrel polishing and sand-blast,etc., then, a terminal electrode paste is burnt to form terminalelectrodes 6 and 8. For example, a firing condition of the terminalelectrode paste is preferably in a mixed gas of wet N₂ and H₂ at 600 to800° C. for 10 minutes to 1 hour or so. In accordance with need,electrical plating, etc. is performed on the terminal electrodes 6 and 8to form a pad layer. Note that the terminal electrode paste may befabricated in the same way as the electrode paste explained above.

A multilayer ceramic capacitor of the present invention produced asabove is mounted on a print substrate, etc. by soldering, etc. and usedfor a variety of electronic equipments.

In a method of producing a multilayer ceramic capacitor according to thepresent embodiment, as a green sheet, a polyvinyl acetal resin having apolymerization degree in a specific range, a butyralation degree in aspecific range and a residual acetyl group amount of a predeterminedvalue or less is used as a binder. Therefore, even an extremely thingreen sheet 10 a of, for example, 5 μm or less is strong enough to bepeeled from the carrier sheet 30 and has preferable adhesiveness andhandlability. Also, surface roughness of the sheet 10 a is small andstackability is excellent. Therefore, it becomes easy to stack a largenumber of green sheets 10 a via electrode layers 12 a, and it is alsopossible to stack without the adhesive layers 28 in accordance withneed.

Also, in a production method of a multilayer ceramic capacitor accordingto the present embodiment, a dry type electrode layer 12 a can be easilyand highly accurately transferred to the surface of the green sheet 10 awithout damaging or deforming the green sheet 10 a.

Furthermore, in the production method of the present embodiment, theadhesive layer 28 is formed on a surface of an electrode layer or agreen sheet by a transfer method, and the electrode layer 12 a isadhered to the surface of the green sheet 10 a via the adhesive layer28. By forming the adhesive layer 28, at the time of transferring theelectrode layer 12 a to the surface of the green sheet 10 a by adhering,a high pressure and heat become unnecessary and adhesion under a lowpressure and low temperature becomes possible. Accordingly, even whenthe green sheet 10 a is extremely thin, the green sheet 10 a is notdamaged, the electrode layer 12 a and the green sheet 10 a can bepreferably stacked, and a short-circuiting defect, etc. is not caused.

In the present embodiment, when a binder composition is same (apolyvinyl butyral resin and/or a polyvinyl acetal resin) in the adhesivelayer 28 and the electrode layer 12 a, adhesiveness between theelectrodes is largely improved. Therefore transfer becomes easy.

Also, for example, by making an adhesive force of the adhesive layer 28stronger than adherence force of the release layer 22 and also makingthe adherence force of the release layer 22 stronger than an adhesiveforce between the green sheet 10 a and the carrier sheet 30, the carriersheet 30 on the green sheet 10 a side can be selectively and easilyremoved.

Furthermore, in the present embodiment, since the adhesive layer 28 isnot directly formed on the surface of the electrode layer 12 a or greensheet 10 a by an applying method, etc. but formed by a transfer method,components of the adhesive layer 28 do not soak in the electrode layer12 a or green sheet 10 a and an extremely thin adhesive layer 28 can beformed. For example, a thickness of the adhesive layer 28 can be made asthin as 0.02 to 0.3 μm or so. Even if the thickness of the adhesivelayer 28 is thin, components of the adhesive layer 28 do not soak in theelectrode layer 12 a or green sheet 10 a, so that the adhesive force issufficient. Moreover, an adverse effect is not given to a composition ofthe electrode layer 12 a or green sheet 10 a.

Also, in the present embodiment, when forming a blank pattern layer 24on a blank pattern portion on the electrode layer 12 a shown in FIG. 2A,viscosity of the blank pattern paste is not extremely declined, andpreferable printing becomes possible even in the case of an extremelythin blank pattern layer. Also, it is not necessary to increase anamount of a binder resin included in the blank pattern paste,delamination, etc. between sheets are not caused at the time of binderremoval of a stacked body.

Particularly, in the present embodiment, a polyvinyl butyral resinand/or a polyvinyl acetal resin is included in the internal electrodepaste, an internal electrode layer 12 a formed by the paste has highstrength and a high adhesive force, and transfer of an adhesive layer 28is relatively easy. Also, when removing a carrier sheet 20 made by a PETfilm as a supporting sheet, breaking of the internal electrode layer 12a is hard to be caused.

Note that the present invention is not limited to the above embodimentsand may be variously modified within the scope of the present invention.

For example, a method of the present invention is not limited to theproduction method of multilayer ceramic capacitors and may be applied asa production method of other multilayer type electronic devices, such asmultilayer inductors, multilayer substrates.

EXAMPLES

Below, the present invention will be explained based on further detailedexamples, but the present invention is not limited to the examples.

Example 1a

Production of Green Sheet Paste

As a starting material of ceramic powder, BaTiO₃ powder (BT-02 made bySakai Chemical Industry Co., Ltd.) was used. A ceramic powdersubcomponent additives were prepared to satisfy (Ba_(0.6)Ca_(0.4))SiO₃:1.48 parts by weight, Y₂O₃: 1.01 parts by weight, MgCO₃: 0.72 parts byweight, Cr₂O₃: 0.13 parts by weight and V₂O₅: 0.045 parts by weight withrespect to 100 parts by weight of the BaTiO₃ powder.

First, only the subcomponents were mixed by a ball-mill to obtainslurry. Namely, the subcomponent additives (total amount 8.8 g) and asolvent (16 g), wherein ethanol/n-propanol is 1:1, were preliminaryground by a ball-mill for 20 hours. Next, the preliminary ground slurryof the subcomponent additives, ethanol: 38 g, n-propanol: 38 g, xylene:28 g, mineral spirit: 14 g, DOP (dioctyl phthalate) as a plasticizercomponent: 6 g and a polyethylene glycol based nonionic dispersant(HLB=5 to 6) as a dispersant: 1.4 g were added to BaTiO₃: 191.2 g andmixed by a ball-mill for 4 hours. Note that a block polymer ofpolyethylene glycol and fatty ester was used as the polyethylene glycolbased nonionic dispersant (HLB=5 to 6) as a dispersant.

The lacqur was-prepared as follow; 15 wt % of BH6 (polyvinyl butyralresin: PVB made by Sekisui Chemical Co., Ltd.) was dissolved inetharol/n-propanol-1/1 solvent system. 80 g of the lacqur was added tothe dispersed paste. After that, by ball-milling, a ceramic paste (forgreen sheet) was obtained.

A polymerization degree of a polyvinyl butyral resin as the binder resinwas 1400, a butyralation degree thereof was 69 mol % ±3 mol %, and aresidual acetyl group amount thereof was 3±2 mol %. The binder resin wascontained by 6 parts by weight in the ceramic paste with respect to 100parts by weight of ceramic powder (including ceramic powder subcomponentadditives). Also, when assuming that total volume of the ceramic powder,binder resin and plasticizer in the ceramic paste was 100 volume %, thevolume ratio accounted by the ceramics powder was 67.31 volume %.

Also, DOP as a plasticizer was contained in the ceramic paste by 50parts by weight with respect to 100 parts by weight of the binder resin.Water was contained by 2 parts by weight with respect to 100 parts byweight of the ceramic powder. The polyethylene glycol based nonionicdispersant as a dispersant was contained by 0.7 part by weight withrespect to 100 parts by weight of the ceramic powder.

Also, in the paste, mineral spirit of at least any one of a hydrocarbonbased solvent, industrial gasoline, kerosene and solvent naphtha wasadded by 5 parts by weight with respect to 100 parts by weight of theceramic powder. Furthermore, the paste contains-an alcohol based solventand an aromatic solvent. When assuming that total weight of the alcoholbased solvent and aromatic solvent was 100 parts by weight, toluene asan aromatic solvent was contained by 15 parts by weight.

Viscosity of the paste was 0.12 Pa.s. The viscosity of the paste wasmeasured by using a Brookfield-type viscosimeter when giving rotation of50 rpm at 25°.

Production of Green Sheet

The paste obtained as above was applied to a PET film as a secondsupporting film shown in FIG. 3A to be a thickness of 5 μm by a wire barcoater and dried to produce a green sheet 10 a. The applying rate was 50m/min. and the drying condition was a temperature in the drying furnaceof 60° C. to 70° C. and drying time of 2 minutes.

Release Layer Paste

A release layer paste obtained by diluting the above dielectric greensheet paste by two times in a weight ratio with ethanol/toluene (55/10).Note that in the release layer, DOP as a plasticizer was contained by 50parts by weight in a ceramic paste with respect to 100 parts by weightof a binder resin.

Adhesive Paste

An adhesive paste was obtained by dissolving 15 wt % of polyvinylbutyral resin into MEK (methylethyl ketone). Additionally,50-part-by-weight plasticizer DOP was added to an adhesive paste, withrespect to 100 parts by weight of dissolved PVB resin.

Internal Electrode Paste (Electrode Paste to be Transferred)

Next, an internal electrode paste was obtained by making slurry bykneading by a ball mill at a composition ratio as shown below. Namely,with respect to 100 parts by weight of Ni particles (electrode materialpowder) having an average particle diameter of 0.2 μm, 20 parts byweight of the same ceramic powder (BaTiO₃ powder and a ceramic powdersubcomponent additives) as ceramic powder contained in the green sheetpaste, 4.5 parts by weight of a polyvinyl butyral resin and 95 parts byweight or terpineol were added and kneaded by a ball mill to makeslurry, so that an internal electrode paste was obtained.

Ni particles as electrode material powder was contained by 47 wt %,which is less than 50 wt %, with respect to the entire internalelectrode paste. As a polyvinyl acetal resin as a binder resin, thosehaving a polymerization degree of 2400 and an acetalization degree of 55mol % were used. The polyvinyl butyral resin is contained by 3.8 partsby weight, which is in a range of 2.5 to 5.5 parts by weight withrespect to a total of 100 parts by weight of the Ni powder and ceramicpowder. Viscosity of the electrode paste composition measured by usingan RV20 type cone disc viscometer made by HAAKE at a shear rate of8[1/s] at 25° C. was 6 Pa.s.

Blank Pattern Paste

A blank pattern paste was produced in the same way as producing aninternal electrode paste. As a binder resin, a polyvinyl butyral resinhaving a polymerization degree of 1450, a butyralation degree of 69 mol% ±3 mol %, and a residual acetyl group amount of 6±2 mol % was used.

Viscosity of the blank paste composition measured by using an RV20 typecone disc viscometer made by HAAKE at a shear rate of 8[1/s] at 25° C.was 7 Pa.s. Also, the paste contained ceramic powder by a ratio of 40 wt% with respect to the entire paste.

Formation of Release Layer and Transfer of Adhesive Layer and ElectrodeLayer

First, to form a release layer, the above release layer paste wasapplied to a PET film (first supporting sheet) by a wire bar coater anddried to form 0.3 μm of a release layer.

On the surface of the release layer, the electrode layer 12 a and theblank pattern layer 24 were formed. The electrode layer 12 a was formedto be a thickness of 1 μm by the printing method by using the aboveinternal electrode paste. The blank pattern layer 24 was formed to be athickness of 1 μm by the printing method by using the above blankpattern paste. At the time of printing by using the blank pattern paste,a problem that the paste flows out from a mesh of a print plate making,etc. were not observed.

Also, an adhesive-layer 28 was formed on another PET film (thirdsupporting sheet). The adhesive layer 28 was formed to be a thickness of0.1 μm by a wire bar coater by using the above adhesive layer paste.

First, on the surface of the electrode layer 12 a and the blank patternlayer 24, the adhesive layer 28 was transferred by a method shown inFIG. 2. At the time of transferring, a pair of rolls were used, thepressure force was 1 MPa, and the temperature was 80° C., and it wasconfirmed that the transfer was preferably performed.

Next, by a method shown in FIG. 3, an internal electrode layer 12 a andblank pattern layer 24 were adhered (transferred) to a surface of thegreen sheet 10 a via the adhesive layer 28. At the time of transferring,a pair of rolls were used, the pressure force was 1 MPa, and thetemperature was 80° C., and it was confirmed that the transfer waspreferably performed.

Adhesive forces of the electrode layer 12 a and the green sheet 10 awere measured in a state shown in FIG. 3B. The adhesive force wasmeasured by respectively releasing the supporting sheets 20 and 30,then, fixing both released surfaces to jigs by using a two-sided tape,respectively, and pulling the jigs up vertically with respect to theadhering surface at a rate of 8 mm/minute, and the maximum stress at thetime was considered as an adhesive force. As shown in Table 1, theadhesive force was 30 N/cm² or more and it was confirmed that a strongadhesive force could be obtained. Note that an adhesive force of 30N/cm² or more could not be measured, because of a measurement limit ofthe measuring jig.

Also, when the carrier sheet 20 made by a PET film was peeled in a stateshown in FIG. 3B, the electrode layer 12 a was not adhered to the sheet20 side and it was clearly peeled off. Namely, as shown in Table 1,there was no problem on the release property (PET release property) ofthe carrier sheet, as well.

Table 1 TABLE 1 Adhesiveness Depending on Electrode Resin Kind andPlasticizer Addition PET PETRelease Strength(mN/cm) Plasticizer AdhesiveRelease Release Dielectric Resin (PHR) Force(N/cm2) Property※※ LayerSide Layer Side Ethyl Comparative Example 1a 0 0 — — — CelluloseComparative Example 1b 50 0 — — — Comparative Example 1c 100 0 — — —Comparative Example 1d 150 5 X(PET, residual) — — Butyral Example 1a0 >30※ ◯ 32.2 3.6 Example 1b 25 >30※ ◯ 29.3 2.0 Example 1c 50 >30※ ◯28.0 2.0 Example 1d 75 >30※ ◯ 27.3 2.6 Example 1e 100 >30※ ◯ 28.0 2.6※30N/cm2 was a measuring limit※※“◯” when no problem is caused by PET release after transfer

Examples 1b to 1e

Other than adding dioctyl phthalate (DOP) as a plasticizer by an addingquantity of 25, 50, 75 and 100 parts by weight to the internal electrodepaste with respect to 100 parts by weight of a binder resin, internalelectrode pastes were fabricated in the same way as in the example 1a,stacked bodies as shown in FIG. 3B were produced, and the same test wasconducted. The results are shown in Table 1.

Also, release strength of the carrier sheets 20 and 30 was measured onthe stacked bodies as shown in FIG. 3B. The results are shown in Table 1and FIG. 10.

Measurement of release strength was obtained by pulling up one end ofthe carrier sheet 20 in the direction of 90-degree with respect to theplane of the stacked body at a rate of 8 mm/minute, for example, in astate shown in FIG. 3B, and measuring a force (mN/cm) acting on thecarrier sheet 20 at the time as the release strength. Since the carriersheet 20 positions on the release layer 22 side, in Table 1 and FIG. 10,the release strength of the carrier sheet 20 is indicated as releasestrength of PET on the release layer side. Also, in the same way,release strength of the carrier sheet 30 is indicated as releasestrength of PET on the dielectric layer side in Table 1 and FIG. 10.

As shown in Table 1 and FIG. 10, the release strength of PET on therelease layer side was confirmed to be lowered by increasing the addingratio PHR (Part Handred of Resin) of DOP. Also, it was confirmed thatresidual of breaking of the electrode layer 12 a is not adhered to thesurface of the carrier sheet 20 after releasing and preferable releasingwas possible.

When releasing the carrier sheets 20 and 30 made by a PET film after drytransfer, if the release strength is too high, breaking of the electrodelayer 12 a and breaking of the adhesive layer 28 are brought. In theelectrode layer of the present embodiment containing a polyvinyl butyralresin, it was confirmed that the release strength could be lowered bybeing added with a plasticizer, such as DOP, as shown in Table 1 andFIG. 10. Namely, the release strength can be lowered to an extent of notcausing a trouble by adding a plasticizer of 25 PHR or more.

Comparative Examples 1a to 1d

Other than using an ethyl cellulose resin instead of a polyvinyl butyralresin as a binder resin of the internal electrode paste, and changing anadding quantity (PHR) of DOP as a plasticizer in a range of 0 to 150parts by weight with respect to 100 parts by weight of the binder resin,internal electrode pastes were fabricated in the same way as in theexample 1b, stacked bodies as shown in FIG. 3B was produced, and thesame test was conducted. The results are shown in Table 1.

As shown in Table 1, when using an ethyl cellulose resin, the adhesiveforce was not improved even if a plasticizer was added, so thatsuperiority of a polyvinyl butyral resin was confirmed.

Note that in Table 1, the adhesive force was 0 in the comparativeexamples 1a to 1c, so that the release property could not be evaluated;and the adhesive force of the comparative example 1d was very low, sothat the carrier sheet 20 could not be released and measurement couldnot be made.

Examples 2a to 2k

As shown in Table 2, other than using a polyvinyl butyral resin or apolyvinyl acetal resin as a binder resin of the internal electrodepaste, changing a polymerization degree, butyralation degree oracetalization degree thereof, and making an adding quantity (metalcontent) of the Ni particles to 45 wt % with respect to the entireelectrode paste, internal electrode pastes were fabricated in the sameway as in the example 1a.

Results of measuring 8% TPO lacquer viscosity in the respective examplesand viscosity of the electrode pastes are shown in Table 2. Theviscosity of the paste was measured by using an RV20 type cone discviscometer made by HAAKE at 25° C., and viscosity (V8(1/s)) when givingrotation of obtaining a shear rate of 8[1/s], and viscosity (V50(1/s))when giving rotation of obtaining a shear rate of 50[1/s] were measured.

Note that in Table 2, the 8% TPO lacquer viscosity means viscosity of avehicle obtained by dissolving 8 parts by weight of a resin in 92 partsby weight of terpineol, and electrode paste viscosity means viscosity ofan electrode paste obtained by compounding powder and a plasticizer,etc. at a predetermined ratio.

To form an electrode layer 12 a of a predetermined pattern as shown inFIG. 2A by the printing method by using the electrode paste, the V8(1/s)viscosity of the paste is 4 Pa.s or higher, and preferably 6 Pa.s orhigher. When the viscosity becomes lower than that, the paste flows outfrom a mesh at the time of printing and blur easily arises, so thatprinting becomes difficult.

From the viewpoint, a polymerization degree of a polyvinyl butyral resinand/or polyvinyl acetal resin to be used for an electrode paste is 1400or more as shown in Table 2.

Also, dry density of the electrode pastes in the examples 2a to 2k wasmeasured, respectively. The results are shown in Table 2. Measurement ofthe dry density was obtained by applying the electrode paste by anapplicator having a gap of 250 μm to form a film, drying at 100° C. for15 minutes, and calculated from a thickness and weight of a certainarea. As shown in the examples 2g, 2i, 2j and 2k, when comparing at thesame polymerization degree, if the acetalization degree of a polyvinylacetal resin becomes high, it is liable that the viscosity becomes highbut the dry density declines. When the dry density declines, continuityand smoothness of electrodes become deteriorated after firing,therefore, the higher, TABLE 2 Table 2: Lacquer Viscosity and ElectrodeViscosity Depending on Resin Kind Butyralation Acetalization 8% TPOLacquer Metal Electrode Paste Viscosity Resin Polymerization degreeDegree Viscosity(Pa · s) Content Viscosity Ratio Dry Density Name Degree(mol %) (mol %) V8(1/s) V50(1/s) (wt %) V8(1/s) V50(1/s) V8/V50 (g/cm3)EC(N50) 26.3 18.2 50 10.7 7.1 1.5 5.6 45 3.9 2.6 1.5 5.5 Example 2a PVB1000 69 10.2 7.1 45 6.0 2.3 2.6 5.6 Example 2b PVB 1450 69 26.0 17.5 4511.2 6.2 1.8 5.6 Example 2c PVB 2400 69 79.3 37.8 45 14.1 8.8 1.6 5.6Example 2d PVB 1400 66 27.6 19.2 45 10.5 5.9 1.8 5.5 Example 2d PVB 170066 65.9 36.2 45 12.8 7.5 1.7 5.5 Example 2e PVB 2000 66 70.4 37.3 4513.9 8.1 1.7 5.5 Example 2g PVB 2400 66 84.5 41.0 45 15.0 9.0 1.7 5.4Example 2h PVB 2000 74 114.7 45.6 45 19.7 10.9 1.8 5.3 Example 2i PVB2400 74 180.7 49.8 45 26.4 13.4 2.0 5.2 Example 2j PVB 2400 55 77.4 38.245 14.9 7.3 2.0 5.6 Example 2k PVB 2400 63 80.2 40.5 45 15.4 7.7 2.0 5.6Viscosity Measurement: RV20 type cone disc viscometer made by HAAKE, at25° C., and shear rate of 8 and 50(1/S)

Comparative Example 2

As shown in Table 2, other than using an ethyl cellulose resin as abinder of the internal electrode paste, and making an adding quantity(metal content) of Ni particles to 45 wt % or 50 wt % with respect tothe entire internal electrode paste, an internal electrode paste wasfabricated in the same way as in the example 1a. The 8% TPO lacquerviscosity and viscosity of the electrode paste of the comparativeexample 2 were measured in the same way as in the examples 2a to 2k. Theresults are shown in Table 2.

As shown in Table 2, when lowering the metal content from 50% to 45% bysolution diluting while fixing a resin amount of the ethyl cellulosebased electrode paste according to the comparative example 2, theviscosity abruptly declines. A paste having this viscosity causes atrouble of blur, etc. in the conventional printing step.

When a content of the Ni particles is 50 wt %, the viscosity becomeshigh even in the case of an ethyl cellulose resin, and printing ispossible, but it becomes difficult to make a thin layer due to the highmetal content.

Examples 3a to 3i

Other than changing an adding ratio (PHP) of a polyvinyl butyral resinto 5.5 to 2.0 parts by weight as shown in Table 3 with respect to atotal of 100 parts by weight of Ni particles and ceramic powder(inhibitor for sintering electrode) in the internal electrode paste,internal electrode pastes were fabricated in the same way as in theexample 1a, stacked bodies as shown in FIG. 3B were produced, andwhether the dry transfer was good or bad was confirmed. Also, aninternal electrode paste of each of the examples was applied by anapplicator having a gap of 250 μm to form a film and dried at 100° C.for 15 minutes, and the dry density was measured. Measurement of thedensity was calculated from a thickness and weight of a certain area.The results are shown in Table 3. TABLE 3 Electrode Paste Dry DensityWhen Changing Resin Amount Resin Amount Paste Dry Breaking PHP/(Ni +Density Dry Transfer Strength Inhibitor) (g/cm3) (good/bad) (MPa)Example3a 6.0 4.8 ∘(Good) 3.0 Example3b 5.5 5.0 ∘(Good) 2.6 Example3c5.0 5.1 ∘(Good) 2.1 Example3d 4.5 5.2 ∘(Good) 2.0 Example3e 4.0 5.4∘(Good) 1.5 Example3f 3.5 5.6 ∘(Good) 1.3 Example3g 3.0 5.7 ∘(Good) 1.0Example3h 2.5 5.9 ∘(Good) 0.8 Example3i 2.0 6.1 x(Bad) 0.5

As shown in Table 3, since the metal filling rate becomes high due to adecrease of a resin amount in the electrode paste, the dry density ofthe electrode paste improves. Note that when the resin amount is toolittle with respect to pigment (Ni+ceramic powder), strength of anelectrode layer declines and a trouble arises in the dry transfer step,so that a resin amount of 3 PHP(Part Handred of Pigment) or more ispreferable.

Namely, as shown in Table 3, when performing dry transfer in the casewhere an adding ratio (PHP) of a polyvinyl acetal resin is less than 2.5PHP, when releasing a PET film as a supporting body, a trouble that theelectrode layer is released while internally broken and adhered to thePET arose. It was indicated by “x” in Table 3. Examples wherein drytransfer was possible were indicated by “o” in Table 3. Note that whenthe adding ratio (PHP) of a polyvinyl butyral resin becomes larger than5.5 PHP, as shown in Table 3, while dry transfer was possible, the pastedry density became 4.8 g/cm³, which was less than 5.0 g/cm³, andbreaking of electrodes increased when stacked and fired, so that it wasnot preferable.

Accordingly, from the results shown in Table 3, it was confirmed that apolyvinyl butyral resin was preferably in a range of 2.5 to 5.5 parts byweight with respect to a total of 100 parts by weight of Ni particlesand ceramic powder.

Also, breaking strength of an electrode layer was measured as below.Namely, as shown in FIG. 2A, at a stage before adhering an adhesivelayer 28 to a surface of an electrode layer 12 a formed by using each ofthe electrode pastes according to the examples 3d to 3i, the carriersheet 20 was peeled and a stacked body of release layers 22 andelectrode layers 12 a was prepared, respectively. The electrode layerside of the each stacked body was supported by two points, a centerposition of the supporting points on the opposite side thereof waspressed by a rod at a rate of 8 mm/minute, and a pressure at the timethat the electrode layer 12 a was broken was measured, and the pressurewas considered as the breaking strength (MPa).

Relationship of an adding ratio of a polyvinyl butyral resin [binderamount PHP/(Ni+ceramic powder)] with respect to a total of 100 parts byweight of Ni particles and ceramic powder and breaking strength is shownin Table 3 and FIG. 9. As shown in Table 3 and FIG. 9, it was confirmedthat as the adding ratio of the polyvinyl butyral resin increased, thebreaking strength improved. An electrode, which can be dry transferred,has breaking strength of 0.8 MPa or more, and adding of a polyvinylbutyral resin by 2.5 PHP or more to the pigment is required to obtainthe breaking strength of 0.8 MPa or more.

As explained above, according to the present invention, it becomespossible to provide an internal electrode paste having enough strengthfor the dry transfer method and adhesive force even when a thickness ofthe green sheet and/or electrode layer is extremely thin. As a result,it is possible to provide an internal electrode paste capable ofeffectively preventing delamination between sheets and deformation of astacked body, etc. and being suitable to making an electronic devicethin and multilayer, and a production method of an electronic device.

1. An internal electrode paste, comprising electrode material powder, abinder resin containing a polyvinyl butyral resin and/or a polyvinylacetal resin as the main component, and a solvent.
 2. The internalelectrode paste as set forth in claim 1, furthermore comprising aplasticizer, wherein said plasticizer is contained by 25 parts by weightor more and 150 parts by weight or less with respect to 100 parts byweight of said binder resin.
 3. The internal electrode paste as setforth in claim 1, wherein said binder resin is contained by 2.5 to 5.5parts by weight with respect to 100 parts by weight of said electrodematerial powder.
 4. The internal electrode paste as set forth in claim1, furthermore comprising ceramic powder.
 5. The internal electrodepaste as set forth in claim 4, wherein said binder resin is contained by2.5 to 5.5 parts by weight with respect to a total of 100 parts byweight of said electrode material powder and ceramic powder.
 6. Theinternal electrode paste as set forth in claim 1, wherein said electrodematerial powder is contained by 50 wt % or less with respect to theentire internal electrode paste.
 7. The internal electrode paste as setforth in claim 1, wherein a polymerization degree of said polyvinylbutyral resin and/or a polyvinyl acetal resin is 1400 or more and 3600or less.
 8. The internal electrode paste as set forth in claim 1 whereinan acetalization degree of said polyvinyl acetal resin is 74 mol % orless.
 9. A production method of an electronic device, comprising thesteps of: preparing the internal electrode paste as set forth in claim1; forming a green sheet; forming an internal electrode layer by usingsaid internal electrode layer paste; stacking said green sheets viainternal electrode layers to obtain a green chip; and firing said greenchip.
 10. A production method of an electronic device, comprising thesteps of: forming an electrode layer on a surface of a first supportingsheet by using the internal electrode paste as set forth in claim 1;pressing said electrode layer against a surface of a green sheet andadhering said electrode layer to the surface of said green sheet;stacking the green sheet adhered with said electrode layer to form agreen chip; and firing said green chip.